Titanium alloys



United States Patent TITANIUM ALLOYS Earl F. Swazy, Richard H. Freyer, and Lee S. Busch, Indianapolis, Ind., assignors, by mesne assignments, to Mallory-Sharon Titanium Corporation, Indianapolis, Ind., a corporation of Delaware No Drawing. Application September 4, 1953, Serial No. 382,183, now Patent No. 2,786,756, dated March 26, 1957, which is a division of application Serial No. 138,516, January 13, 1950, now Patent No. 2,661,286, dated December 1, 1953. Divided and this application February 15, 1957, Serial No. 644,429

2 Claims. (Cl. 75-175.5)

This invention relates generally to alloys of titanium and has particular reference to alloys consisting of titanium, carbon and silicon, alone, or in combination with another element, to form a quaternary alloy with titanium predominating. This application is a divisional application of Serial No. 382,183, filed September 4, 1953, now Patent No. 2,786,756, dated March 26, 1957, which in turn is a division of application Ser. No. 138,516, filed January 13, 1950, now Patent No. 2,661,286, dated December 1, 1953.

An object of the present invention, therefore, is to provide wrought, ductile alloys of titanium.

Another object of the present invention is to provide a wrought, ductile alloy of titanium, carbon and silicon.

Still another object of the invention is to provide quaternary alloys of titanium.

Yet another object of the invention is to provide alloys of titanium consisting of titanium, carbon and silicon having greater resistance to oxidation at elevated temperatures than pure titanium and exhibiting good hardness characteristics thereof.

Another object of the invention is to provide an alloy of titanium consisting of titanium, carbon and silicon and any one of the following elements: aluminum, copper, vanadium, chromium, boron, tungsten and iron.

Yet another object of the invention contemplates a method of preparing quaternary alloys of titanium consisting of the ternary alloys of carbon, silicon and titanium, to which is added an element from the group: aluminum, copper, chromium, vanadium, boron, tungsten or iron.

The invention, in another of its aspects, relates to the novel features and principles teaching the objects of the invention and to the novel principles employed herein whether or not these features and principles may be used in said object or in said field.

It is found that alloys of titanium, silicon and carbon with titanium predominating as a ternary alloy, or as an alloy to which may be added another element such as aluminum, chromium, copper, vanadium, boron, tungsten or iron provide a resistance to oxidation at elevated temperatures greater than that of pure titanium. Such alloys provide ductile, strong alloys of titanium and exhibit good corrosion resistance and high hardness characteristics at elevated temperatures. These alloys are usually manufactured by melting and casting in a graphite retort under an inert or neutral atmosphere; for example, argon, or in a vacuum. Further, the alloys may also be prepared by powder metallurgy methods. Thus, as an example, alloys containing .1% to silicon, .2% to 2% carbon with the balance titanium, as compared to pure titanium, are characterized by having a higher tensile strength, equivalent ductility, slightly higher electrical resistivity, much better resistance to oxidation at elevated temperatures and high hardness at temperatures up to 600 C. Further they may be hot or cold worked by the usual methods known to the art.

As a further example, hereof, an alloy made by mixing ice silicon powder and titanium powder or sponge, and melting and casting in graphite in argon gas, contained 0.992% silicon, .47 carbon, with the balance titanium. This alloy had the following properties as hot forged to reduction in area (equivalent properties of titanium Moreover, alloys, such as above, are characterized by a unique response to heat treatment. Upon quenching from 1000 C., these alloys do not harden appreciably (most alloys of titanium which contain metals forming stable carbides do harden on quenching). However, as the tensile strength is lowered to 113,500 p. s. i., the elongation increases to 16.5%. In the as forged condition, the hardness at 600 C. increases from 0 Rockwell A to 32 Rockwell A when quenched. These changes are apparently caused by the presence of large amount of B titanium (body centered cubic) which is not transformed to a on fast cooling from 1000 C.

Again, in resistance to sealing tests at 900 C., an alloy containing 992% silicon was three times as efiective as that for titanium containing .47% carbon. The results revealed a 536% increase in Weight for the silicon alloy and 1.89% for the titanium alloy containing carbon only.

A quaternary alloy which may be fabricated from the ternary alloys of titanium, carbon and silicon is the alloy of boron, silicon, titanium and carbon. Alloys thus formed are ductile and are stronger than pure titanium. They have considerably better resistance. to oxidation at elevated temperatures and like the other quaternary alloys described exhibit better corrosion resistance and higher hardness at elevated temperatures than those of pure titanium. For example, the resistance to oxidation at 900 C. is found to be much better than pure titanium or titanium with carbon present only. The alloys of titanium, silicon, boron and carbon may be fabricated as described 'by the methods above; such as melting and casting in an inert and neutral atmosphere (for example, argon) or in a vacuum. These alloys, too, may be prepared by powder metallurgy methods. Thus, a preferred method consists of mixing silicon and boron in massive or powder form with titanium in sponge or powder form and melting and casting in a graphite crucible. Since the source of the carbon is the crucible, the amount is easily controlled by varying the time the charge is molten. The alloys may be forged in air at temperatures between 800 C. to 900 C. and may be hot or cold Worked by the methods known to the 'art.

The alloys of titanium, carbon, silicon and boron as here described, may be made consisting of small but significant amounts of silicon, boron and carbon: that is, up to 5% silicon; up to 5% boron; and up to 2% carbon; the balance being titanium. A practical range of composition is .5% to 3% silicon; 0.5% to 2.0% boron; 0.3% to 0.7% carbon; the balance being titanium.

These alloys have the following minimum properties in the hot forged condition:

Ultimate tensile strength p. s. i 120,000 Elongation in 2" percent 10 Modulus of elasticity p. s. i 15 x10 Electrical resistivity ohm-cm 65 10-5 T1, per- Si, per- 0, per- Alloy cent cent cent and- (1) Ti, Si, C 99. 7-88 110 .2-2- (6) Ti, Si, O B 99. 7-88 1-5 1-2 15% B Thus, it is seen that by the present invention primary, ductile, ternary alloys of titanium, silicon and carbon may be formed presenting characteristics substantially superior to pure titanium in matters of resistance to oxidation, resistance to corrosion and high hardness. In addition, these ternary alloys may be combined with boron. Thus, a basic ternary alloy consists of from .1% to 10% silicon; from .2% to 2% carbon with the remainder being substantially all titanium. Further, quaternary alloys of titanium, silicon, carbon and boron may be fabricated wherein the. silicon is present in amounts up to-5%; carbon in amounts up to 2%;. boron in amounts up to 5% 5 of the alloy, the remainder of the total amount being supplied by the titanium.

While the present invention as to its objects is merely illustrative and not exhaustive in scope and since many widely different embodiments of the invention may be made without departing from the scope thereof, it is intended that all matter contained in the above description be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. Alloys containing from 0.1% to 5% silicon, from 0.1% to 5% boron, from 0.1% to 2% carbon,-and. the balance substantially all titanium.

2. Alloys'of titanium as in claim 1 having the following minimum properties:

Ultimate tensile strength p. s. i 120,000 Elongation in 2 pcrcent 10 Modulus of elasticity p. s. i- 15x10 Electrical resistivity ohm-cm 65 xii)? No references cited. 

1. ALLOYS CONTAINING FROM 0.1% TO 5% SILICON, FROM 0.1% TO 5% BORON, FROM 0.1% TO 2% CARBON, AND THE BALANCE SUBSTANTIALLY ALL TITANIUM. 